The technology of the present disclosure relates to an optical scanning device and an image forming apparatus including the same.
In the related art, there has been known an optical scanning device mounted in an electrophotographic image forming apparatus. The optical scanning device emits light beams corresponding to image data at a predetermined writing timing and allows the light beams to be scanned on a surface of a photosensitive drum.
The optical scanning device includes a casing, a light source provided in the casing, a deflector that deflects light beams emitted from the light source and converts the light beams into scanning light, an image forming lens that allows an image of the scanning light from the deflector to be formed on a photosensitive drum, a synchronization detection mirror provided out of an effective scanning region (out of a scanning region for image formation) of the light beams having passed through the image forming lens, and a synchronization detection sensor that detects light beams reflected by the synchronization detection mirror.
The synchronization detection sensor detects the light beams and outputs a synchronization signal serving as a reference of a writing timing of image data toward a control unit. The control unit controls a writing timing of an image to the photosensitive drum based on a reception timing of the synchronization signal.
In such a type of optical scanning device, when the temperature inside the casing increases during its operation, position shift of the light beams in a main scanning direction occurs due to extension and contraction of the image forming lens, a change in a refractive index and the like. As a consequence, there is a problem that, for example, position shift of an image occurs in a monochromatic apparatus and color shift occurs in a color machine.
In order to solve such problems, there has been proposed an optical scanning device having a correction mechanism. The correction mechanism, for example, rotates the synchronization detection mirror in accordance with a change in the temperature inside the casing to adjust a light beam detection time by the synchronization detection sensor, and to correct shift of a writing position of the image data in the main scanning direction. The correction mechanism has a support member that supports one end part of a reflecting mirror so as to be rotatable, an extendable member that is extended and contracted by temperature and rotates the reflecting mirror about the support member, and an urging member that urges the reflecting mirror to the extendable member side.